1. Technical Field
This device relates to automatic discharge valves used in condensate traps associated with fluid pressurized systems. It is required to drain accumulated condensate from the traps so that the system will remain free of intrained moisture that persist during compression and expansion of gases under pressure.
2. Description of Prior Art
Prior art devices of this type have been known as float controlled condensate traps which increases the possibility of valve sticking which allows loss of gas or air under pressure within the system. Prior art devices have also utilized timer activated purge valves which can become independent from actual condensate levels within the traps again allowing for an unwanted loss of pressure. Sensing systems have been developed that rely on two condensate sensors with a trap to indicate low and high condensate levels within. Single sensor probes have also been illustrated that contain two sensing elements in a single probe body allowing for reliable selective activation and auditing of the purge valve by separate sensing elements within, see for example U.S. Pat. Nos. 1,681,344, 3,429,329 3,675,673, 4,261,382, 4,308,889, 4,336,821 and 4,914,626.
In U.S. Pat. No. 1,681,344 a condensate removing system is shown wherein an auxiliary condensate discharge pipe and discharge valve utilizes a differential of pressure between supply header and discharge header requiring an unbalance of air pressure for condensate to be purged from the system.
U.S. Pat. No. 3,429,329 is directed to a drain apparatus for automatically draining condensate which determines when condensate collects in the drain pipe the differential head pressure between the drain pipe and the chamber exert pressure on an air trap. The weight of the diaphragm is thus overcome and the air pilot valve closes to shut off flow of compressed air to the discharged valve. The pressure in the discharge valve is reduced and the fluid is discharged through the drain pipe.
U.S. Pat. No. 3,675,673 is directed to a pressure activated drain valve responsive to differential and fluid viscosity i.e. air and water.
In U.S. Pat. No. 4,261,382 a condensate drain valve is disclosed wherein single and multiple sensors are positioned within fluid transfer system to activate an electronic circuit for drain valve operation. Once a probe is covered with condensate, a positive output is achieved to an integrated circuit that compares same with an inherent value within the circuit opening the main valve within a timing event circuit.
U.S. Pat. No. 4,308,889 is directed to an electric conductive type steam trap having a condensate level detecting apparatus connected to a control circuit that activates a solenoid valve discharging the condensate. The valve activation is timed for closing after a pre-determined time element has expired after the condensate detecting probe is free of condensate. The probe is a simple on/off signal activation device.
U.S. Pat. No. 4,336,821 discloses a solenoid activated drain valve in which the valve element is a differential piston exposed on opposite faces to reservoir pressure normally holding the valve closed and minimizing the opening force required to be exerted by the solenoid. A temperature responsive heating element protects the valve from freezing while a sensing element determines the presence of water allowing the valve to operate.
Finally, in U.S. Pat. No. 4,974,626 a condensate trap valve is shown utilizing two sensors positioned in vertically spaced relation to one another in a single tube within a condensate accumulation chamber. As the first sensor is submerged in condensate a signal is formed indicating low level and it is the differential in contact between the two sensors which determine an activation of the condensate trap valve within the system.